Micromechanical components, which are used, for example, in the automotive field as inertial or pressure sensors, normally have a microstructure including movable functional elements. The microstructure is also designated as a MEMS structure (microelectromechanical system). During the operation of the sensors, a deflection of a functional element is detected, for instance, via a change in the electrical capacitance with respect to a fixed reference electrode.
A current method for manufacturing a micromechanical component includes forming the microstructure on a functional substrate and joining the functional substrate to a cap substrate, through which a hollow space (cavity or cavern) surrounding the functional elements of the microstructure is formed. A metallic or eutectic wafer bonding process may be carried out to join the two substrates. For such a joining technique, frame-shaped connecting structures, also known as a “bonding frame” or “bonding layer,” which have metallic materials or materials matched to one another for the formation of a eutectic alloy, may be formed on the upper surfaces of the two substrates. In the bonding process, the individual connecting structures are joined to form a common connecting structure, thereby forming a hermetically tight seal situated around the microstructure.
In the case of the functional substrate, the connecting structure is produced prior to forming the microstructure. However, the “topography” associated with the connecting structure or “material plane” projecting from the upper surface of the functional substrate has an adverse influence on the production of the microstructure, during which a photolithographic patterning method is used. A result of the presence of the connecting structure situated about the subsequent microstructure is that in this region, the photoresist used in the patterning method cannot be deposited or spun on uniformly, and therefore makes waves or is subject to variations in thickness. In a subsequent exposure step, the uneven photoresist may cause unwanted scattering effects, through which (lateral) dimensions of the structures to be produced are subject to fluctuations. Such variations in structure width have a directly negative effect on the microstructure and, consequently, on the electrical properties of the sensor. The steady reduction in structural dimensions and the decrease in reserves or the distance between the connecting structure and microstructure increasingly amplifies this negative effect.